1. Field of the Invention
An aspect of the present invention relates to at least one of an image processing device and an image processing method.
2. Description of the Related Art
As a typical noise that degrades image quality, a granularity or a tone jump is known. A granularity refers to a pattern like a fine dot to be found in a flat area of an image and a tone jump refers to a state that a tone discretely changes in an image.
Because such a noise is caused more explicitly in a case where image processing such as a tone transformation is executed, it is desirable to preliminarily reduce the noise by using a smoothing filter or the like.
However, in a case where a smoothing filter or the like is used, there is a problem that a detail of an image, such as a texture or an edge, is impaired, although it is possible to suppress a “noise” on an image such as a granularity or a tone jump. Accordingly, an image processing technique is desired that is capable of reducing a noise while a detail is maintained.
Herein, for example, Japanese Patent No. 3939428 proposes an image processing technique capable of reducing a noise while an edge is maintained, wherein an edge-preserving smoothing process is executed for original image data and a differential value is calculated between post-processing image data and pre-processing original image data.
However, in a case of an image processing technique disclosed in Japanese Patent No. 3939428, it is not possible to maintain a texture although an edge as a detail is maintained. This is because it is not possible to extract a high-frequency image such as a texture from original image data by merely executing an edge-preserving smoothing process and calculating a differential value between before and after the process so that it is not possible to eliminate only a noise.